Summary Background The insect brain can be divided into neuropils that are formed by neurites of both local and remote origin. The complexity of the interconnections obscures how these neuropils are established and interconnected through development. The Drosophila central brain develops from a fixed number of neuroblasts (NBs) that deposit neurons in regional clusters. Results By determining individual NB clones and pursuing their projections into specific neuropils we unravel the regional development of the brain neural network. Exhaustive clonal analysis revealed 95 stereotyped neuronal lineages with characteristic cell body locations and neurite trajectories. Most clones show complex projection patterns, but despite the complexity, neighboring clones often co-innervate the same local neuropil(s) and further target a restricted set of distant neuropils. Conclusions These observations argue for regional clonal development of both neuropils and neuropil connectivity throughout the Drosophila central brain.

Labeling every neuron in a lineage in the fruit fly olfactory system reveals that every cell is born with a pre-determined cell fate that is invariant and dependent upon neuron birth order

Summary The Drosophila central brain develops from a fixed number of neuroblasts. Each neuroblast makes a clone of neurons that exhibit common trajectories. Here we identified 15 distinct clones that carry larval-born neurons innervating the Drosophila central complex (CX), which consists of four midline structures including the protocerebral bridge (PB), fan-shape body (FB), ellipsoid body (EB), and noduli (NO). Clonal analysis revealed that the small-field CX neurons, which establish intricate projections across different CX substructures, exist in four isomorphic groups that respectively derive from four complex posterior asense-negative lineages. About the region-characteristic large-field CX neurons, we found that two lineages make PB neurons, ten lineages produce FB neurons, three lineages generate EB neurons, and two lineages yield NO neurons. The diverse FB developmental origins reflect the discrete input pathways for different FB subcompartments. Clonal analysis enlightens both development and anatomy of the insect locomotor control center.

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SUMMARY Activity-dependent modifications strongly influence neural development. However, molecular programs underlying their context and circuit-specific effects are not well understood. To study global transcriptional changes associated with chronic elevation of synaptic activity, we performed cell-type-specific transcriptome profiling of Drosophila ventral lateral neurons (LNvs) in the developing visual circuit and identified activity-modified transcripts that are enriched in neuron morphogenesis, circadian regulation, and lipid metabolism and trafficking. Using bioinformatics and genetic analyses, we validated activity-induced isoform-specific upregulation of Drosophila lipophorin receptors LpR1 and LpR2, the homologs of mammalian low-density lipoprotein receptor (LDLR) family proteins. Furthermore, our morphological and physiological studies uncovered critical functions of neuronal lipophorin receptors (LpRs) in maintaining the structural and functional integrities in neurons challenged by chronic elevations of activity. Together, our findings identify LpRs as molecular targets for activity-dependent transcriptional regulation and reveal the functional significance of cell-type-specific regulation of neuronal lipid uptake in experience-dependent plasticity and adaptive responses.